The present invention relates to a display driver.
In recent years, a high-speed serial transfer interface such as a low voltage differential signaling (LVDS) interface has attracted attention as an interface aiming at reducing EMI noise or the like. In such a high-speed serial transfer, data is transferred by causing a transmitter circuit to transmit serialized data using differential signals and causing a receiver circuit to differentially amplify the differential signals.
A known portable telephone includes a first instrument section provided with buttons for inputting a telephone number or characters, a second instrument section provided with a display panel or a camera, and a connection section (e.g. hinge) which connects the first and second instrument sections. Therefore, the number of interconnects passing through the connection section can be reduced by transferring data between a first substrate provided in the first instrument section and a second substrate provided in the second instrument section by serial transfer using differential signals. JP-A-2001-222249 (US2002/0011998A1) discloses a technology of performing serial transfer in portable telephone using differential signals.
A display driver (LCD driver) is known which drives a display panel such as a liquid crystal panel. In order to realize high-speed serial transfer between the above-mentioned first and second instrument sections, a high-speed interface circuit which transfers data through a serial bus must be incorporated in the display driver.
However, when the display driver is mounted using a chip on glass (COG) technology, the signal quality of high-speed serial transfer deteriorates due to contact resistance at a bump as an external connection terminal.
A reduction in chip size is required for the display driver in order to reduce cost. On the other hand, the size of the display panel incorporated in a portable telephone or the like is approximately the same. Therefore, if the chip size is reduced by merely shrinking the display driver using a microfabrication technology, it becomes difficult to mount the display driver.